1. Field of the Invention
The present invention is related to an ultrasonic diagnosing apparatus used so as to perform medical diagnosing operations by transmitting ultrasonic waves toward an object to be inspected, and by receiving ultrasonic echoes reflected from the object.
2. Description of a Related Art
In medical fields, various types of imaging techniques have been developed in order to observe and diagnose interior portions of an object to be inspected. In particular, as to ultrasonic imaging techniques capable of acquiring internal information of an object to be inspected by transmitting/receiving ultrasonic waves to/from the object, ultrasonic image observations can be carried out in real time, and furthermore, there is no risk that the object is exposed by radioactive rays, which is different from other medical imaging techniques using X-ray photography, RI (radio isotope) scintillation cameras or the like. As a consequence, the ultrasonic imaging techniques are utilized as imaging techniques having higher safety characteristics in very broad fields which may involve the obstetrics and gynecology department, the circulatory organ department and the digestive department as well as fetus diagnosis in the obstetrical department.
However, in an actual case, there are many unknown aspects with respect to adverse influences caused by ultrasonic waves given to biological bodies. For example, as techniques using energy of ultrasonic waves, the following methods are known. That is, in a cure, cancerous cells of biological bodies are destroyed by employing strong focused ultrasonic waves. In an ultrasonic homogynizer, cavitation is generated by employing strong focused ultrasonic waves so as to stir or crash samples. In a heat-curing device, heating effect achieved by ultrasonic waves are utilized. While such a nature of ultrasonic waves is considered, even when very weak ultrasonic waves are utilized in ultrasonic imaging operations, or even when high frequency ultrasonic waves are utilized, a certain adverse influence given to biological bodies may be predicted. Also, according to current research reports, ultrasonic examinations executed while woman is pregnant may give adverse influences to the fetus. As a result, it is preferable that intensity of ultrasonic waves which irradiate the object during ultrasonic imaging operations must be suppressed to minimum necessary intensity.
By the way, in an ultrasonic imaging operation, an irradiation intensity of ultrasonic waves is expressed by an MI (medical index value). In recent general-purpose ultrasonic diagnosing apparatus, such a function is provided by which irradiation intensity of ultrasonic waves is controlled by setting the MI value. However, the adverse influences of ultrasonic waves to the biological bodies are caused not only by intensity of these ultrasonic waves. For instance, the previously-explained heating effect of ultrasonic waves is related to the ultrasonic irradiation amount which is obtained both the intensity of ultrasonic waves and the irradiation time thereof.
An ultrasonic irradiation amount is also changed depending upon a scanning method employed when an ultrasonic imaging operation is carried out. For instance, in an M-mode imaging operation, since ultrasonic waves continuously irradiate one portion, a total ultrasonic irradiation amount at the same portion of a biological body is increased. In contrast, in a B-mode imaging operation, although this imaging operation requires long operation time, since an irradiation direction of ultrasonic waves is always changed, a total ultrasonic irradiation amount at one portion is small. Furthermore, in accordance with a color Doppler mode, since ultrasonic waves having high intensity irradiate the object along the same direction many times, an entire ultrasonic irradiation amount is increased.
As previously explained in the case where adverse influences of ultrasonic waves to an object to be inspected are considered, there is an important aspect. That is, not only intensity of these ultrasonic waves, but also a total amount of ultrasonic waves which irradiate the object for a constant time period must be considered. However, conventionally, such an ultrasonic diagnosing apparatus capable of counting an ultrasonic irradiation amount or capable of controlling such an ultrasonic irradiation amount has not yet been developed. Also, when an MI value is set to a lower MI value in order to suppress an ultrasonic irradiation amount, intensity of a received signal is also lowered. As a result, there is a problem that an S/N ratio in ultrasonic images is also uniformly lowered, so that the image qualities are deteriorated.
The present invention has been made to solve the above-described problems, and therefore, has an object to provide such an ultrasonic diagnosing apparatus capable of decreasing a total amount of ultrasonic waves which irradiate an object to be inspected for a constant time period, while image qualities of ultrasonic images are not deteriorated.
To solve the above-described problem, an ultrasonic diagnosing apparatus according to a first aspect of the present invention comprises: ultrasonic transmitting and receiving means for transmitting ultrasonic waves in accordance with an applied voltage and receiving ultrasonic echoes reflected from an object to be inspected; input means for inputting information related to an irradiation amount of ultrasonic waves; and irradiation amount control means for adjusting a frame rate on the basis of the irradiation amount information input via the input means so as to control an irradiation amount of ultrasonic waves which irradiate the object.
Here, the frame rate corresponds to a transmission rate of ultrasonic waves which are transmitted plural times in order to acquire ultrasonic images, and is expressed by a number of frames acquired per second.
In accordance with the first aspect of the present invention, since the ultrasonic irradiation amount is controlled not by adjusting the irradiation intensity but by adjusting the frame rate, the ultrasonic irradiation amount can be suppressed to a lower ultrasonic irradiation amount without deteriorating image qualities.
Further, an ultrasonic diagnosing apparatus according to a second aspect of the present invention comprises: ultrasonic transmitting and receiving means for transmitting ultrasonic waves in accordance with an applied voltage and receiving ultrasonic echoes reflected from an object to be inspected; accumulating means for accumulating an irradiation amount of ultrasonic waves transmitted from the ultrasonic transmitting and receiving means to obtain an accumulated value; and irradiation amount control means for adjusting a frame rate on the basis of a relationship between the accumulated value obtained by the accumulating means and a preset value so as to control an irradiation amount of ultrasonic waves which irradiate the object.
According to the second aspect of the present invention, while the ultrasonic imaging operation is carried out, the ultrasonic irradiation amount is accumulated. When the accumulated value reaches a preset value, the frame rate is lowered, so that it is possible to avoid excessive irradiation of ultrasonic waves.
In this application, an ultrasonic irradiation amount implies such a value which is obtained by integration intensity of ultrasonic waves irradiating an object to be inspected by time.